glsl/standalone: init EmptyUniformLocations

This updates the scaffolding to reflect init_shader_program() and
will be required in the following patch to avoid a segfault.

Reviewed-by: Alejandro Piñeiro <apinheiro@igalia.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/30034>

src/compiler/glsl/standalone_scaffolding.cpp

@@ -307,6 +307,8 @@ standalone_create_shader_program(void)
    whole_program->FragDataBindings = new string_to_uint_map;
    whole_program->FragDataIndexBindings = new string_to_uint_map;
 
+   exec_list_make_empty(&whole_program->EmptyUniformLocations);
+
    return whole_program;
 }